Process for preparing spirocyclic phosphorus compounds

ABSTRACT

Bis(2-hydroxyalkyl) N,N-di(lower-alkyl)aminomethylphosphonates are described. These phosphorus-containing polyols can be incorporated into polyurethane foams to render the latter fire retardant. They have the advantage over closely related phosphorous-containing polyols that they are autocatalytic in the polyurethane foam forming reaction and that they can be mixed with the polyol component of the polyurethane foam forming composition to give a mixture (premix) which can be maintained in storage for prolonged periods without showing any signs of deterioration.

This is a division of application Ser. No. 786,690 filed Apr. 11, 1977now U.S. Pat. No. 4,112,014, which latter is a continuation ofapplication Ser. No. 634,136, filed Nov. 21, 1975 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to novel polyols and to processes for theirpreparation and is more particularly concerned with novelphosphorus-containing polyols and with processes for their preparationand with their use in the preparation of fire retardant foams.

2. Background of the Invention

A prodigious amount of research has been devoted in recent years to thedevelopment of phosphorus-containing compounds which possess activehydrogen containing groups such as hydroxyl and amino and which can,therefore, be incorporated chemically into polyurethane and likepolymers. The incorporation of such phosphorus containing compounds intopolymers generally results in some degree of enhancement of the flameretardant properties of the polymer. However, many of the phosphoruscontaining compounds so investigated have proved to be of no practicalimportance because of undesirable side effects such as an adverse changein physical properties of the resulting polymer, incompatibility withthe other components of the polymer forming mixture, and the like.

One of the more successful groups of phosphorus compounds of the abovetype, which has been developed and widely used in imparting fireretardance to polyurethane foams, is that represented by the formula:##STR1## within this group the compound diethylN,N-di(2-hydroxyethyl)-aminomethylphosphonate is widely known and usedcommercially; see U.S. Pat. No. 3,076,010.

Unfortunately, this compound and the class to which it belongs share adisadvantage which is common to many other potentially useful phosphoruscontaining polyols in that they are unstable when stored for extendedperiods of time in combination with other components normally employedin the fabrication of polyurethanes. It is common practice to supply twocomponent systems for the manufacture of polyurethanes, one componentbeing a polyisocyanate or an isocyanate-terminated prepolymer, and thesecond component being a mixture of polyols, surfactants, catalysts, andthe like additives. The two components are stored separately until it isdesired to produce the desired polyurethane at which point the twocomponents are mixed and allowed to react.

When a phosphorus containing polyol, such as the particular onesdiscussed above, is to be employed in a two component system for theproduction of polyurethanes, it is desirable to include it as part ofthe component which contains the polyol and other ingredients.Obviously, the phosphorus-containing polyol cannot be incorporated inthe polyisocyanate component because of the interaction which would takeplace. It is, therefore, desirable that any phosphorus polyol which isto be employed in the above manner be stable when stored in admixturewith the polyol and other ingredients of the polyol component. It is anobject of the invention to provide a phosphorus-containing polyol whichmeets this criterion and which is also capable of imparting fireretardant properties to polyurethanes without exerting any deleteriouseffects on the physical properties of the latter. Other objects of theinvention will become apparent as the description of the inventionproceeds.

Many compounds closely related chemically to the known compounds offormula (I) above have been described in the art. Illustratively, U.S.Pat. No. 3,314,957 shows bis(dialkylene glycol)dialkylaminomethanephosphonates and related compounds and their use inthe synthesis of polyurethanes. Substantially the same group ofcompounds is also disclosed in U.S. Pat. Nos. 3,549,728, 3,457,333 and3,539,536 both show the corresponding bis(hydroxypolyalkoxyalkyl)N,N-di(hydroxyalkyl)aminomethanephosphonates and their use in thesynthesis of fire retardant polyurethanes. U.S. Pat. Nos. 3,480,594 and3,480,699 show O-(hydroxyalkoxy)-O'-hydroxyalkylN,N-di(hydroxyalkyl)aminomethanephosphonates and fire retardantpolyurethanes derived therefrom. U.S. Pat. No. 3,567,801 showsgenerically, but not specifically, di(hydroxyalkoxy)aminomethanephosphonates in which the two nitrogen atoms can beunsubstituted. U.S. Pat. No. 3,707,587 is concerned with a process forpreparing, inter alia, di(hydroxyalkyl)N,N-di(hydroxyalkyl)aminomethanephosphonates by reacting dialkanolamineswith spirocyclic phosphorus compounds obtained, for example, by reactingalkylene-1,2-glycols with trialkylphosphites.

We have now found that a certain narrow class of esters ofN,N-disubstituted aminomethanephosphoric acid possess properties whichare highly advantageous and which distinguish them from the many suchesters of this class hitherto known.

SUMMARY OF THE INVENTION

This invention comprises O,O'-bis(2-hydroxyalkyl)N,N-di(lower-alkyl)aminomethanephosphonates having the formula: ##STR2##wherein R₁, R₂, R₃ and R₄ are each independently selected from the groupconsisting of hydrogen and lower-alkyl, and R₅ and R₆ each independentlyrepresents lower-alkyl.

The invention also comprises storage stable polyol component premixeswhich contain the above compounds (II) and which are adapted for use inmulti-component systems for the preparation of polyurethanes.

The invention also comprises flame retardant polyurethanes derived fromthe compounds (II) and more particularly those in which the compounds(II) serve as part of the polyol component and also serve as catalystsin the polyurethane forming reaction.

The term "lower-alkyl" is used herein in its conventionally acceptedsense as meaning alkyl having from 1 to 6 carbon atoms, inclusive, suchas methyl, ethyl, propyl, butyl, pentyl, hexyl and isomeric formsthereof.

DETAILED DESCRIPTION OF THE INVENTION

The compounds of the formula (I) are obtained conveniently by reactionof the corresponding spirocyclic phosphorus compounds of the formula:##STR3## wherein A, A', B and B' are independently selected from thegroup consisting of hydrogen and lower-alkyl, with formaldehyde and theappropriate di(lower-alkyl)amine R₅ R₆ NH under Mannich reactionconditions. The above formula (III) represents only one of a number ofpossible isomers which can occur when A, A', B, B' or any of them areother than hydrogen, because of the stereoisomerism about the phosphorusatom. The formula (III) has been used for the sake of simplicity torepresent all the possible isomers which are obtained in the preparationof this compound by the methods which will be described hereinafter.

The above reaction is represented schematically as follows:

    (III)+CH.sub.2 O+HNR.sub.5 R.sub.6 →                (II)

It will be seen that the reaction leads to ring opening of thespirocyclic phosphorus compound (III) to form the hydroxyalkyl estergroups which are represented in the formula for compound (II) asHO--CHR₁ --CHR₂ -- and HO--CHR₃ --CHR₄ -- wherein R₁, R₂, R₃ and R₄ areas hereinbefore defined. It will also be seen that each of the two ringsin the spirocyclic phosphoric compound (III) can open in either of twoways, i.e. either at linkage (a) or linkage (b) in the case of the onering and at linkage (a') or (b') in the case of the other ring.Illustratively, ring opening at linkage (a) will give rise to the group##STR4## whereas opening of the same ring at linkage (b) will give riseto the group ##STR5## Similar ring opening of the other ring in compound(III) at linkage a' will give rise to the group ##STR6## and ringopening at linkage b' will give rise to the group ##STR7##

It is believed that the product obtained in the above reaction is amixture of products some of which are derived by ring opening atlinkages a and a', some by ring opening at linkages b and b' and some byring opening at combinations of a and b' or b and a'. Accordingly, theproduct obtained in any instance has been designated by formula (II) andit is to be understood that this formula, except in the case whereineach of R₁, R₂, R₃ and R₄ represent hydrogen, encompasses a mixture ofthe various possible products derived by ring opening of the spirocycliccompound (III) in the various ways discussed above. Analyticaltechniques presently available do not permit of a quantitative analysisof the proportions of the various possible isomeric forms of thehydroxyalkyl groups in the compound (II).

The reaction between the spirocyclic phosphorus compound (III), theformaldehyde and the secondary amine HNR₅ R₆ is carried out readily bybringing the reactants together in substantially equimolar proportions.The reaction conditions employed are those of the well-known Mannichreaction; see, for example, Organic Reactions, Adams, Vol. 1, pp.303-330, Wiley, New York, New York, 1942. Preferably the spirocyclicphosphorus compound (III) and the formaldehyde are brought togetherfirst in any convenient manner and the secondary amine is added to theresulting mixture. The reaction is generally exothermic although it isgenerally necessary to provide heat initially to promote the reaction.Thus the initial mixture of the compound (III) and formaldehyde can beheated to about 60° C. or higher before addition of the secondary aminebegins and thereafter the temperature of the reaction mixture isadvantageously maintained in the range of about 50° C. to about 80° C.until reaction is complete. The latter occurrence can be determinedreadily by routine analytical procedures, for example, by observing thedisappearance of the absorption band corresponding to the P-H bond inthe infrared absorption spectra of an aliquot of the reaction mixture.

If desired the above reaction can be carried out in the presence of aninert organic solvent such as methylene chloride, benzene,chlorobenzene, toluene, xylene, carbon tetrachloride and the like.However, the use of such solvents is generally unnecessary unless it isotherwise difficult to control the exotherm generated in the reaction.

The desired product (II) is isolated from the reaction product obtainedas described above by removing the more volatile products bydistillation advantageously under reduced pressure. The product soobtained generally contains traces of acid material. It is believed thatthe latter arises during the reaction by the formation of small amountsof compounds having free hydroxyl groups attached to phosphorus, whichcompounds arise during ring opening of the spirocyclic phosphoruscompound (III). Irrespective of the cause of formation of the acidity,it is desirable to eliminate said acidity in the product. This can bedone by any of the conventional methods known in the art for eliminatingacidity in polyols. Advantageously, the acidity is corrected by reactingthe crude product (II), obtained as described above, with a minor amountof an alkylene oxide, preferably propylene oxide.

The proportion of alkylene oxide required will vary from batch to batchof the product (II) since the amount of acidity will vary. Theproportion of alkylene oxide required in any given instance can readilybe determined by trial and error. It is important to note that thereaction of the compound (II) with the alkylene oxide under theconditions employed does not involve any significant reaction of thealkylene oxide with the hydroxyl groups of the hydroxyalkyl radicals insaid compounds.

After the above described treatment, the compound (II) obtained asdescribed above is then ready for use in the preparation ofpolyurethanes, and of polyol component premixes therefor, as will bedescribed in more detail hereafter.

The spirocyclic phosphorus compounds (III) are, in many cases, knowncompounds and all can be prepared by methods known in the art; see, forexample, U.S. Pat. No. 3,707,587. We have found that, in addition to themethod described in the latter reference, which method involves thereaction of propyleneglycol-1,2 or any corresponding vicinal alkanediolwith trimethylphosphite, the compound (III) can be prepared by a noveland relatively inexpensive procedure which will now be described. Thisprocess can be represented schematically as follows: ##STR8## A, A', Band B' have the significance hereinbefore defined.

The various steps shown above can be carried out in a single continuousmanner without the need to isolate the various intermediates. In theinitial step the alkylene glycol (IV) is added slowly, with agitationand under an atmosphere of inert gas such as nitrogen, to the phosphorustrichloride. The reactants are employed in approximately equimolarproportions. The temperature of the reaction mixture is maintainedadvantageously in the range of about 0° C. to 25° C. and preferably inthe range of 5° C. to 10° C. during the addition and thereafter untilthe desired reaction is found to be complete as determined by routineanalytical procedures such as infrared spectroscopy. The resultingproduct (V) is then maintained in the same range of temperaturedescribed above while an approximately equimolar proportion of propyleneoxide is added.

When the addition is complete, i.e. the second step shown above iscomplete, the final step of the process is accomplished by addition,with agitation, of an approximately equimolar proportion of the secondalkylene glycol (VI). This second alkylene glycol can be the same as theinitial glycol (IV) or can be different. The temperature during thisfinal addition is again maintained in the same range as that employed inthe previous steps. The resulting reaction mixture is maintained in saidtemperature range until the reaction is adjudged to be complete asdetermined by routine analytical procedures such as infraredspectroscopy. The desired product (III) is isolated from the reactionproduct by stripping of volatile materials by distillation,advantageously under reduced pressure. The product (III) can bepurified, if desired, by conventional procedures such as chromatography,distillation and the like.

The phosphorus containing polyols (II) of the invention can be employedin the preparation of polyurethanes and thereby impart fire retardancethereto. The methods conventionally employed in the art for thepreparation of polyurethanes can be employed in preparing fire retardantpolyurethanes in accordance with this invention. The novel feature isreplacement of part of the polyol conventionally employed by anequivalent amount of a phosphorus containing polyol (II) or a mixture oftwo or more such polyols. The amount of the polyol (II) which isemployed in this manner is advantageously sufficient to impart to theresulting polyurethane a content of phosphorus in the range of about 0.5to about 3 percent. This content of phosphorus in the final product isachieved by employing from about 0.05 to about 0.3 equivalents of thephosphorus containing polyol (II), or a mixture of two or more suchpolyols, per equivalent of the polyisocyanate employed in the reactionmixture.

While the use of the phosphorus-containing polyols (II) can be appliedto the formation of any type of polyurethane, including cellular andnon-cellular polyurethanes, it is of particular application to thepreparation of cellular polyurethanes both flexible and rigid as well asthose foams which are intermediate between the two and are commonlyreferred to as semi-flexible or semi-rigid. A comprehensive account ofthe techniques conventionally employed in the art for the preparation ofcellular and non-cellular polyurethanes by the interaction ofpolyisocyanates and polyols, is to be found in Saunders and Frisch,Polyurethanes, Chemistry and Technology, Part II, 1964, IntersciencePublishers, New York. These techniques are so well-known and familiar toone skilled in the art that it is unnecessary to give a detailed accountthereof.

Thus, any of the polyisocyanates and polyols conventionally employed inthe art can be used in preparing polyurethanes in accordance with thisinvention provided that a portion of the polyol component, within thelimits discussed above, is replaced by the phosphorus containing polyolof formula (II). Illustrative of the organic polyisocyanates are2,4-toluene diisocyanate, 2,6-toluene diisocyanate,4,4'-methylenebis(phenyl isocyanate), 2,4'-methylenebis(phenylisocyanate), dianisidine diisocyanate, tolidine diisocyanate,hexamethylene diisocyanate, m-xylylene diisocyanate, 1,5-naphthalenediisocyanate, p-phenylene diisocyanate,1,4-diethylbenzene-β,β'-diisocyanate, tri(4-isocyanatophenyl)methane,and other di- and higher polyisocyanates such as those listed in thetables of Siefken, Annalen, 562, 122-135, 1949. Mixtures of two or moreof the above isocyanates can be used, such as mixtures of the 2,4- and2,6- isomers of toluene diisocyanate, mixtures of 2,4'- and4,4'-methylenebis(phenyl isocyanate) and the like.

In addition to the various isomers of methylenebis(phenyl isocyanate)and mixtures of these isomers, there can also be used modified forms ofthese isocyanates. For example, there can be used4,4'-methylenebis(phenyl isocyanate), or an admixture thereof with aminor amount of the 2,4'-isomer, which has been treated to convert aminor proportion, generally less than 15 percent by weight of thestarting material, to an artefact of the latter. For example, thepolyisocyanates employed in making the polyurethane foams of theinvention can be methylenebis(phenyl isocyanate) which has beenconverted to a stable liquid form in accordance with the process of U.S.Pat. No. 3,384,653. Illustrative of another form of modifiedmethylenebis(phenyl isocyanate) is the product obtained by treating4,4'-methylenebis(phenyl isocyanate), or mixtures thereof with the2,4'-isomer, with a minor proportion of a carbodiimide such asdiphenylcarbodiimide in accordance with the process described in BritishPat. No. 918,454.

In addition to the di- and higher polyisocyanates illustrated above, theorganic polyisocyanates employed in the preparation of the polyurethanefoams of the invention include the isocyanate-terminated prepolymersobtained by reacting an excess of any of the polyisocyanates discussedabove with a polyol. The polyols employed in making theisocyanate-terminated prepolymers can be any of those conventionallyemployed in the art for this purpose. Advantageously, said polyols havean hydroxy equivalent weight of about 30 to about 2,000 and afunctionality from 2 to 4. Preferably, said polyols are diols, i.e. havea functionality of 2.

The polyols employed in making polyurethane foams in accordance with theprocess of the invention can be polyester or polyether polyols,advantageously those having a functionality from 2 to 6 and anequivalent weight from 90 to about 2000. Illustrative of the polyetherpolyols are polyoxyalkylene glycols such as polytetramethylene glycol,the polyoxyethylene glycols prepared by the addition of ethylene oxideto water, ethylene glycol or diethylene glycol; polyoxypropylene glycolsprepared by the addition of 1,2-propylene oxide to water, propyleneglycol or dipropylene glycol; mixed oxyethylene oxypropylene glycolsprepared in a similar manner utilizing a mixture of ethylene oxide orpropylene oxide or a sequential addition of ethylene oxide and1,2-propylene oxide; polyether glycols prepared by reacting ethyleneoxide, propylene oxide, or mixtures thereof with mono- and polynucleardihydroxybenzene, e.g. catechol, resorcinol, hydroquinone, orcinol,2,2-bis(p-hydroxyphenyl)propane, bis(p-hydroxyphenyl)methane and thelike; and polyethers prepared by reacting ethylene oxide, propyleneoxide, or mixtures thereof with aliphatic polyols such as glycerol,trimethylolpropane, 1,2,6-hexanetriol, and the like.

Illustrative of polyester polyols are those prepared by polymerizingε-caprolactone using an initiator such as ethylene glycol, ethanolamineand the like, and those prepared by esterification of polycarboxylicacids such as phthalic, terephthalic, succinic, glutaric, and adipicacids and the like, with polyhydric alcohols such as ethylene glycol,butanediol, glycerol, trimethylolpropane, 1,2,6-hexanetriol and thelike.

As set forth above the phosphorus containing polyols of the formula (II)are autocatalytic, i.e. they will catalyze the reaction between thepolyisocyanate and the polyol without the need for other catalysts to beemployed. However, in certain instances, for example, where a very fastreaction is desired or where the proportion of compound (II) employed inthe polyurethane forming reaction is low, it may be necessary to includea conventional polyurethane catalyst in the reaction mixture. Many suchcatalysts are known; see, for example, Saunders et al., ibid, Part I,pages 228-232 and Britain et al., J. Applied Polymer Science, 4, pp.207-211, 1960. Illustrative of these catalysts are organic and inorganicsalts of, and organometallic derivatives of, bismuth, lead, tin, iron,antimony, uranium, cadmium, cobalt, thorium, aluminum, mercury, zinc,nickel, cerium, molybdenum, vanadium, copper, manganese, and zirconium,as well as phosphines and tertiary organic amines. Representativeorganotin catalysts are stannous octoate, stannous oleate, dibutyltindioctoate, dibutyltin laurate, and the like. Representative tertiaryorganic amine catalysts are triethylamine, triethylenediamine,N,N,N',N'-tetramethylethylenediamine,N,N,N',N'-tetraethylethylenediamine, N-methylmorpholine,N-ethylmorpholine, N,N,N',N'-tetramethylguanidine,N,N,N',N'-tetramethyl-1,3-butanediamine, N,N-dimethylethanolamine,N,N-diethylethanolamine, and the like. Preferred catalysts for use inthe process of the invention are triethylamine and triethylenediamine.The amount of catalyst employed, if one is present in addition to thecompound (II), is generally within the range of about 0.1 to about 2percent by weight based on total weight of reactants.

The blowing agents which are employed in preparation of the polyurethanefoams of the invention can be any of those conventionally employed inthe preparation of rigid polyurethane foams. Illustrative of saidblowing agents are water (which generates carbon dioxide by reactionwith isocyanate) and volatile solvents such as the lower molecularweight aliphatic hydrocarbons and highly halogenated lower-aliphatichydrocarbons, for example, trichloromonofluoromethane,dichlorodifluoromethane, chlorotrifluoromethane,1,1-dichloro-1-fluoroethane, 1-chloro-1,1-difluoro-2,2-dichloroethane,and 1,1,1-trifluoro-2-chloro-2-fluorobutane and the like. If desired, amixture of water and one or more of said volatile solvents can be usedas blowing agent. The final foam density of the rigid polyurethane foamsproduced by the process of the invention is a function of the amount ofblowing agent used. In general the higher the amount of blowing agent,the lower the density of the foam.

Optional additives such as dispersing agents, cell stabilizers,surfactants, flame retardants, and the like which are commonly employedin the preparation of rigid polyurethane foams can be employed inpreparation of the foams of this invention. Thus a finer cell structurecan be obtained if water-soluble organosilicone polymers are used assurfactants. Organosilicone polymers obtained by condensing apolyalkoxypolysilane with the monoether of a polyalkylene ether polyolin the presence of a acid catalyst are representative of thosesurfactants which can be used for this purpose. Other surfactants suchas ethylene oxide modified polypropylene ether glycols can be used, ifdesired, to obtain better dispersion of the components of the foammixture.

Other additives such as dyes, pigments, soaps and metallic powders andother inert fillers can be added to the foam mixture to obtan specialfoam properties in accordance with practices well-known in the art.

As discussed above, the compounds of the formula (II) display, as one oftheir many advantages, the ability to form storage stable polyolpremixes. The latter are commonly employed as one component of amulticomponent system which is supplied as such to the ultimate user.The various component of the system are not admixed until it is desiredto prepare the desired polyurethane. Thus, the various components of thepolyurethane forming system may be stored over prolonged periods beforeuse. It is eminently desirable that no change in properties,particularly in regard to relative reactivity of the polyol componentincluding catalyst and the polyisocyanate, occur during storageotherwise the reaction occurring when the components are ultimatelybrought together may not proceed as desired and the properties of theresulting polyurethane may not correspond to expectations.

We have found that the polyols of the formula (II) can be stored inadmixture with the polyol, a catalyst if one is employed, and otherconventional additives set forth above, all of which materials areconventionally employed as a single blend in the polyol premix ofmulticomponent systems, and the premix so obtained shows no signs ofdeterioration after storage over periods of many months. Thus, evenafter prolonged storage, the premixes in question show no significantchange in reactivity rates, as measured by cream time and rise time inthe case of foams, in the reaction with the polyisocyanate component toform the desired polyurethane. Further, the physical properties ofpolyurethanes derived by reaction of the polyisocyanate and polyolpremix, after the latter have been stored for long periods, show nosignificant differences from those of polyurethanes prepared byinteraction of the polyisocyanate and polyol premix shortly after thelatter has been prepared.

These properties of the phosphorus containing polyols (II) of theinvention distinguish them from the various closely related polyolshitherto known in the art. In particular the storage stability and theautocatalytic activity of the polyols (II) distinguish them from thecommonly used phosphorus containing polyols of formula (I) above.

The following examples describe the manner and process of making andusing the invention and set forth the best mode contemplated by theinventors of carrying out the invention but are not to be construed aslimiting.

EXAMPLE 1

Dimethyl-1,4,6,9-tetraoxa-5-phospha(5-P^(V))spiro[4,4]nonane

To a solution of 352 ml. (4 mole) of phosphorus trichloride in 800 ml.of methylene chloride maintained at 10° C. was added, with stirring, atotal of 304 g. (4 mole) of propanediol-1,2. The addition was madeslowly but continuously over a period of 1 hour. The resulting productwas maintained at 8° to 12° C. and stirred while a total of 265.2 g.(4.4 mole) of propylene oxide was added over a period of about 20minutes. The resulting mixture was stirred and maintained at the sametemperature for a further period of 15 minutes. Thereafter the excesspropylene oxide was removed by reducing the pressure in the system toabout 15 mm. of mercury and maintaining this pressure for approximately15 minutes. A total of 304 g. (4 mole) of propanediol-1,2 was then addedto the residue with stirring. The temperature rose to a maximum of 40°C. The mixture so obtained was then allowed to stand at room temperature(circa 20° C.) overnight before being subjected to distillation underreduced pressure, finally at 50°-60° C. and 0.3 mm. of mercury, toremove volatile materials. There was thus obtained 785 g. ofdimethyl-1,4,6,9-tetraoxa-5-phospha(5-P^(V))spiro[4,4]nonane in the formof an oily liquid.

EXAMPLE 2

O,O'-di(hydroxypropyl) N,N-diethylaminomethanephosphonate

A mixture of 270 g. (1 mole) ofdimethyl-1,4,6,9-tetraoxa-5-phospha(5-P^(V))spiro[4,4]nonane and 45 g.(1.5 mole) of paraformaldehyde was heated, with stirring, to 50° C. anda total of 115.3 g. (1.58 mole) of diethylamine was added slowly over aperiod of 2.5 hr. The temperature during the addition was maintained at55°-60° C. When the addition was complete, it was found that someformaldehyde was still present in the reaction mixture. The temperatureof the mixture was raised to 75° C. and a total of 25 ml. (0.24 mole) ofdiethylamine was added with stirring. After a period of 30 minutes, themixture was subjected to distillation at 50° to 60° C. and a pressure of0.3 mm. to remove volatile material. The residue was found by acid-baseindicator to exhibit slight acidity. Accordingly, the product was heatedto 60° C. and 25 ml. (0.37 mole) of propylene oxide was added. Theresulting mixture was maintained at 60° C. for 1 hour and again testedfor acidity. Slight acidity was detected and accordingly a secondtreatment with propylene oxide was carried out in exactly the samemanner. After the treatment was complete, excess propylene oxide wasremoved under reduced pressure. The resulting product exhibited nosignificant acidity. There was thus obtained 432.8 g. (quantitativeyield) of O,O'-di(hydroxypropyl) N,N-diethylaminomethanephosphonate,wherein the hydroxy propyl groups were mixtures of the isomeric formsrepresented by ##STR9## in the form of a liquid having a hydroxylequivalent of 135 (theory 141.5).

Anal.: Calcd. for C₉ H₂₂ O₅ NP: C, 46.64; H, 9.19; N, 4.95; P, 10.95Found: C, 46.8; H, 9.6; N, 5.4; P, 9.3

EXAMPLE 3

O,O'-di(hydroxypropyl) N,N-dimethylaminomethanephosphonate

A mixture of 270 g. (1.5 mole) ofdimethyl-1,4,6,9-tetraoxa-5-phospha(5-P^(V))spiro[4,4]nonane and 45 g.(1.5 mole) of paraformaldehyde was heated to 55° to 60° C. with stirringand a total of 67.5 g. (1.5 mole) of dimethylamine gas was passed intothe mixture with stirring over a period of 3 hours. The temperature ofthe reaction mixture was maintained in the range of 55° to 60° C.throughout the addition. When the addition was complete, the temperatureof the reaction mixture was raised to 65° C. for 15 minutes and theresulting mixture was allowed to cool to room temperature (circa 20° C.)and was maintained thereat overnight. Volatile materials were removedfrom the product by distillation under reduced pressure. The residueexhibited slight acidity by response to acid-base indicator and wastherefore heated to 50° C., 30 ml. of propylene oxide was added and themixture was agitated at about 60° C. for 45 minutes before removing theexcess propylene oxide under reduced pressure. The resulting productshowed no significant acidity. There was thus obtained 375.6 g. (98%theoretical yield) of O,O'-di(hydroxypropyl)N,N-dimethylaminomethanephosphonate, wherein the hydroxy propyl groupswere mixtures of the isomeric forms represented by ##STR10## in the formof a liquid having a hydroxyl number of 104 (theory 127.5).

Anal.: Calcd. for C₉ H₂₂ O₅ NP: C, 42.35; H, 8.63; N, 5.49; P, 12.16Found: C, 42.2; H, 8.6; N, 4.7; P, 10.4

EXAMPLE 4

Using the procedure described in Example 3, but replacing thedimethylamine there used by an equivalent amount ofN-ethyl-N-methylamine, diisopropylamine, N-methyl-N-pentylamine, anddihexylamine, there were obtained the O,O'-di(hydroxypropyl)esters ofN-ethyl-N-methylaminophosphonic, N,N-diisopropylaminophosphonic,N-methyl-N-pentylaminomethanephosphonic andN,N-dihexylaminomethanephosphonic acids.

EXAMPLE 5

Three polyol premixes for use in a rigid polyurethane foam formingsystem were prepared by intimately blending the following components inthe proportions (all parts by weight) stated.

    ______________________________________                                        Premix               A       B       C                                        ______________________________________                                        Amine based polyol.sup.1                                                                           75      75      75                                       Diethyl N,N-di(2-hydroxyethyl)-                                               aminomethanephosphonate                                                                            25      --      --                                       Phosphorus polyol of Example 2                                                                     --      25      --                                       Phosphorus polyol of Example 3                                                                     --      --      25                                       Triethylamine        1.31    1.31    --                                       Water                0.45    0.45    0.45                                     Silicone surfactant.sup.2                                                                          2.0     2.0     2.0                                      Trichlorofluoromethane                                                                             40.2    40.2    40.2                                     ______________________________________                                         Footnotes:                                                                    .sup.1 Polyol (eq. wt. = 131) obtained by blending (i) a polyol obtained      by propoxylating a polymethylene polyphenyl polyamine containing              approximately 50 percent by weight of methylenedianiline and (ii) a polyo     (eq. wt. = 89) obtained by propoxylating glycerol.                            .sup.2 DC193: Dow Corning.                                               

It will be seen that Premix A contained a fire retardant polyol widelyused commercially and Premixes P and C contained phosphorus containingpolyols of the invention. Premix B contained a tertiary amine catalystin addition to the phosphorus containing polyol, whereas Premix C didnot.

Within 24 hours of their preparation, a portion of each premix was usedto prepare a rigid foam by reaction with a polymethylene polyphenylpolyisocyanate having an equivalent weight of 133.5 and containingapproximately 50 percent by weight of methylenebis(phenyl isocyanate).The amount of polyisocyanate employed in each case was sufficient togive a ratio of NCO/OH of 1.42:1. This high ratio of NCO/OH is a featureof the particular system under test which is designed to give a lowdensity rigid foam when poured in place in cavities in which the foam isrequired to rise for an extended distance in the vertical direction. Itis a system in which the risk of degradation of the phosphoruscontaining polyol is high due to presence of water in the polyol premix.

The remainder of each of the premixes was then stored for a total of 6months at room temperature at the end of which time the preparation ofthe foams was repeated using the same polyisocyanate. The data given inTable I below shows the reaction times exhibited by the three premixesbefore and after storage. It will be seen that the reaction times forPremixes B and C were substantially unchanged after six month's storage,whereas the reaction times for Premix A had increased substantiallyafter storage for 6 months. This change (a lowering of reactivity)reflects significant deterioration of the Premix during storage.

                  TABLE I                                                         ______________________________________                                        Premix Reaction Times                                                          Before Storage     After Storage for 6 Months                                Time  Premix           Premix                                                 (secs.)                                                                             A        B        C    A      B      C                                  ______________________________________                                        Mix    10       10       10    10    10     10                                Cream  45      30        40   60    30      50                                Gel   195      90       140  330    80     160                                Rise  235      130      220  420    150    230                                ______________________________________                                    

The reaction times exhibited by Premix C illustrate the auto-catalyticactivity of the polyol of the invention included therein, said activitybeing clearly within the practically useful range for polyurethanecatalysts.

The properties of the foams derived from the above premixes afterstoring for less than 24 hours were as follows. The properties of thefoams obtained after storage for 6 months in accordance with thisparticular experiment were not determined.

    ______________________________________                                        Foam Properties                                                                              Foam Premix                                                                   A      B         C                                             ______________________________________                                        Density: Pcf.    1.53     1.54      1.56                                      Compressive strength                                                          parallel to rise; psi                                                                          11.9     11.5      14.7                                      % change in volume                                                            (a) after aging at                                                            158° C. and 100%                                                       humidity                                                                      1 day            6.4      4.8       6.3                                       3 days           8.5      7.2       9.2                                       7 days           8.8      5.9       9.8                                       14 days          10.6     6.0       13.0                                      (b) after aging at                                                            200° F. and ambient                                                    humidity                                                                      3 days           2.3      2.8       4.7                                       7 days           4.4      1.6       3.9                                       Oxygen index                                                                  (ASTM D-2863)    24.5     25.0      25.1                                      ______________________________________                                    

EXAMPLE 6

1,4,6,9-tetraoxa-5-phospha(5-P^(V))spiro[4,4]nonane.

To a solution of 44 ml. (0.5 mole) of phosphorus trichloride in 100 ml.of methylene chloride was added, slowly with stirring and cooling, atotal of 31 g. (0.5 mole) of anhydrous ethylene glycol. The addition wascomplete in 15 minutes. The temperature of the reaction mixturethroughout the addition was maintained at 6° C. The resulting productwas stripped of solvent by distillation under reduced pressure and theresidue was then distilled in vacuo to obtain 47.6 g. (75.3%theoretical) of 2-chloro-1,3-dioxa-phospholane in the form of a fumingcolorless liquid having a boiling point of 38° at 10 mm. of mercury.

A solution of 9.7 g. (0.077 mole) of the above compound in 20 ml. ofmethylene chloride was stirred and maintained at a temperature of about15° C. while a total of 5.8 g. (0.1 mole) of propylene oxide was addedover a period of about 5 minutes. The resulting mixture was stirred andmaintained at the same temperature for a short period before removingexcess propylene oxide by reducing the pressure in the system to about15 mm. of mercury. To the resulting product was added slowly, withstirring, a total of 4.8 g. (0.077 mole) of ethylene glycol. The mixtureso obtained was stirred for approximately 15 minutes before removing themethylene chloride and other volatiles by distillation under reducedpressure. There was thus obtained 10.6 g. (90.6% overall yield) of1,4,6,9-tetraoxa-5-phospha(5-P^(V))spiro[4,4]nonane in the form of asolid.

EXAMPLE 7

Using the procedure described in Example 6, but replacing the ethyleneglycol used in the second step by propylene-1,2-glycol, there wasobtained 2 (or3)-methyl-1,4,6,9-tetraoxa-5-phospha(5-P^(V))spiro[4,4]nonane.

Similarly using the procedure described in Example 6, but replacing theethylene glycol used in the second step by butane-1,2-diol andhexane-1,2-diol, there are obtained 2 (or 3)-ethyl and 2 (or3)-butyl-1,4,6,9-tetraoxa-5-phospha(5-P^(V))spiro[4,4]nonane,respectively.

EXAMPLE 8

Using the procedure described in Example 1, but replacing thepropylene-1,2-diol used in each step by butane-1,2-diol andhexane-1,2-diol, there are obtained diethyl- anddibutyl-1,4,6,9-tetraoxa-5-phospha(5-P^(V))spiro[4,4]nonane,respectively.

EXAMPLE 9

O,O'-di(2-hydroxyethyl) N,N-dimethylaminomethanephosphonate.

Using the procedure described in Example 3, but replacing thedimethyl-1,4,6,9-tetraoxa-5-phospha(5-P^(V))spiro[4,4]nonane there usedby an equimolar amount of1,4,6,9-tetraoxa-5-phospha(5-P^(V))spiro[4,4]nonane (prepared asdescribed in Example 6) there was obtained O,O'-di(2-hydroxyethyl)N,N-dimethylaminomethanephosphonate in the form of a liquid. Theidentical material, made by a different synthetic route, was found tohave the following analysis.

Calcd. for C₇ H₁₆ O₅ NP: C, 37.00; H, 7.92; N, 6.16; P, 13.65 Found: C,37.43; H, 8.21; N, 4.91; P, 13.06

EXAMPLE 10

A rigid polyurethane was prepared using the procedure described inExample 5 but employing the following reactants and proportions (allparts by weight):

    ______________________________________                                        Amine based polyol (Ex. 5)                                                                            80                                                    Di(2-hydroxyethyl) N,N-                                                       dimethylaminomethane-                                                         phosphonate             20                                                    Triethylamine (Ex. 9)   2                                                     Organosilicone surfactant                                                                             2                                                     Trichlorofluoromethane  31                                                    Polymethylene polyphenyl                                                      polyisocyanate (Ex. 5)  129                                                   ______________________________________                                    

The resulting foam had excellent cell structure and appearance and wassubstantially free of odor. A corresponding foam made exactly asdescribed above, but replacing the di(2-hydroxyethyl)N,N-dimethylaminomethanephosphonate by diethylN,N-di(2-hydroxyethyl)aminomethanephosphonate, had a pronounced odorcharacteristic of the phosphorus polyol.

We claim:
 1. A process for the preparation of a spirocyclic phosphoruscompound of the formula: ##STR11## wherein A, A', B and B' are eachindependently selected from the class consisting of hydrogen andlower-alkyl, which comprises admixing substantially equimolarproportions of phosphorus trichloride and a diol ##STR12## wherein A andA' are as above defined, at a temperature within the range of 0° C. to15° C., maintaining the resulting reaction product at a temperaturewithin the same range while adding at least an equimolar proportion ofpropylene oxide thereto, and, finally, maintaining the product soobtained at a temperature range of about 25° C. to about 40° C. whileadding an equimolar proportion of a second diol ##STR13## wherein B andB' are as above defined.
 2. A process according to claim 1 wherein thediol employed in both stages is propylene-1,2-diol and the productobtained isdimethyl-1,4,6,9-tetraoxa-5-phospha(5-P^(V))spiro[4,4]nonane.
 3. Aprocess according to claim 1 wherein the diol obtained in both stages isethylene glycol and the product obtained is1,4,6,9-tetraoxa-5-phospha(5-P^(V))spiro[4,4]nonane.